The proposed experiments build on a program of research aimed at understanding the potentials and limits of effective cognitive functioning during the adult years. Specific aims of the proposed research are 1) to describe cognitive aging in terms of the factors that regulate the rate of skill acquisition, and 2) to describe age differences in the relative efficiency of selected forms of skill learning (item learning, rule learning, feature learning, context learning, and sequence learning). Performance of younger and older adults under conditions that contrast forms of learning (e.g., simple item learning with rule learning) is expected to provide tests of general theories as well as developmental theories of skill acquisition. During the five years of this project, about 1000 women and men between the ages of 20 and 70 years will be tested in eight experiments. Experiments 1-4 examine age-related differences in the effects of practice on item learning, computational speedup, and the shift from computation to item learning under conditions that favor either item learning or computation. Experiments 5-7 are designed to contrast different forms of learning with one other so as to weigh the contribution of each to overall skill. The data from Experiments 5-7 will allow specific age deficits in learning to be identified, and will exploit those deficits to test general theories of learning and automatization. Experiment 8 investigates inter-session disruption and retention effects by age. The outcomes of the proposed research contribute to the understanding of the effective conditions of skill acquisition and retention throughout the adult life span.